U.S. Pat. No. 6,901,729; U.S. patent application Ser. No. 10/822,465, filed Apr. 12, 2004; U.S. Provisional Application No. 60/699,271, filed Jul. 14, 2005; and U.S. Provisional Application No. 60/699,548, filed Jul. 15, 2005, are each incorporated herein by reference in its entirety.
The present invention relates generally to harvesting machines of the type that require flotation systems for permitting their headers to ride lightly up and over rises in the terrain during field operation, and particularly to a hydraulic header lift and flotation system for such a machine that will provide the dual functions of header lift and flotation.
Header flotation systems typically use extension springs, either hydraulically or manually adjusted, bell cranks and other linkages to provide the desired function. The structure generally requires numerous components and large extension springs, and it is quite difficult to develop the mechanical components required to float the broad range of header sizes available even requiring different tractors or frames having their own flotation systems designed to meet their own particular header weight requirements.
Some manufacturers are using an accumulator and hydraulic cylinders to perform the flotation function. These machines typically use separate hydraulic cylinders for the lift and flotation functions, and they lack the capability of independently adjusting the flotation force for each side of the header. Additionally, some headers are not inherently balanced side to side. Special considerations must be made to float and lift these headers evenly by adding ballast, which can become unreasonably heavy or awkward, or modifying the lift geometry of one side.
It would be quite beneficial to have a header lift and flotation system that employs a single hydraulic cylinder for each side of the header, simplifying the controls and mechanical components necessary to perform these functions. It would also be beneficial to have an automatic capability for controlling the hydraulics to put the header of a windrower into a raised transport mode under certain specific conditions.